[racket] define-judgment-form and non-s-expression

This looks like a bug to me, but I'm a define-judgment-form newbie:

(define-language L)
(define-judgment-form L
   #:mode (f I O)
   [(f any any)])

 > (judgment-holds (f 2 2))
#t
 > (judgment-holds (f #hash() #hash()))
#f

Is it a bug or just an inherent limitation on judgments?

David